String.split(regex, limit) uses regex as the implementation and returns java.util.regex.Pattern.compile(regex).split(this, limit).
A simple use of String.split (e.g. the regex is just one character-delimiter) will need to initialize the regex engine and load many regex classes that is pretty heavy-weight.
Most of the String.split calls from the JRE implementation are the simple case e.g. regex parameter is "=", ":", ",", "\0", "\\|"
We can implement a lightweight version of String.split for these simple regex to avoid loading the regex engine. Alternatively, if feasible, implement a lightweight version of the regex support so that String.replaceAll, String.replaceFirst, String.replace(CharSequence, CharSequence), and String.matches can take advantage of such optimization.